THE PARALLAX OF FIXED STARS. 165 



The star 1830 of Groombridge's catalogue (right as- 

 cension llh. 44m. 18s., declination 38 48' north), has the 

 largest proper motion at present known, exceeding 7 ff in 

 arc ; and in .consequence various attempts have been made 

 at different places to determine its parallax, the prob- 

 ability being great that its parallax would be appre- 

 ciable. The discovery of the proper motion was pub- 

 lished by Argelander in the year 1842, and Bessel was 

 induced to give immediate directions to Schliiter, his 

 assistant, to commence a series of measures with the 

 Konigsberg heliometer. These measures were begun in 

 October, 1842, and were terminated abruptly near the end 

 of August, 1843, by the illness and subsequent death of 

 Schliiter. M. Wichmann was then charged with the con- 

 tinuation of the observations, but more pressing duties 

 prevented him from completing the observations till the 

 year 1851. 



In the year 1846 Mr. Faye, by observing with the 

 equatorial of the Paris observatory the difference of right 

 ascension between this star and that of another small star 

 situated nearly on the same parallel, determined the 

 parallax to be 1".08, and by this striking result drew the 

 attention of others to the star. Peters, by discussion of 

 his observations made at Pulkova with. Ertel's circ]e r 

 subsequently determined its parallax to be 0".226, with a 

 probable error of OM41. This result is derived from 48 

 zenith distances observed in 1842 and 1843. Mr. Wich- 

 mann's discussion of Schliiter's observations gave a parallax 

 of OM8. M. Otto Struve, by micrometer measures of 



